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  1. #1

    Cold/Hot start issue/trouble. Garage smell. Tank venting? Check valve failure?

    2001 GP1200R

    I've been troubleshooting a small cold and hot start issue for a few weeks. When I bought the ski it started up very very easily, but now its more of a throttling chore. Especially when cold, it can take 10~15 seconds to go with various degree of choke and aggressive throttling. Once started the engine runs just fine. I don't doubt the carbs need to be rebuilt as they are due, but now I think I found a different issue attributing to the problem. I've heard that in order to have better starting, the tank needs to be under some pressure. Enough so that when opening the fuel fill cap, the tank should vent at the gas cap when loosened. I only remember my ski venting 1~2 times since I've owned it 2 months.

    I store the ski in my garage on a dolly, and since ownership I've been greeted with a faint smell of fuel odor in the garage. A quick door lift and the smell just goes away. At first I thought it was the general smell of a noxious marine 2-stroke engine just sitting in the garage, or perhaps the smell of silicon spray preserving the 3-cyl engine... but now I'm not so sure its natural - smells a bit more like faint, unburnt, gasoline.

    So, I pull the front bin out, and take a look at the tank and lines coming off. I decide to try my best to pressure test the system, so I pull the line off the air separator to the tank - including the "one-way check valve". I hook my bicycle pump up to the tank and give it a few pumps - a couple of PSI and the tank holds air tight as my bicycle pump gauge barely rests off of 0psi. Releasing the pump and the tank vents right out where the pump connected. I blow through the water separator side and its straight through - now I understand the system. The tank should vent inward from the outside - where the water separator is just there I guess in case the ski flips or from water splashing.

    A few rids ago under a very full tank - my friend said he smelt some unburnt fuel. I shrugged and said "Its a 2-stroke" and went on. Now I think it may have actually been leaking or just heavily venting on the water.

    The one-way check valve at the top of the tank was sticking - Only if I blew through it very hard did it stop the flow in one direction. Hmm something is wrong with it me thinks... I give it a few shots of carb cleaner and PB blast to it, but now I cant get it to seal one way at all - its like a straight pass-through in-line coupler. I believe this part is now the culprit. Its supposed to be one-way correct? If so, this may start to put an end to the smell in the garage and the cold/hot start problem.


    Tonight I just plugged the top of the tank in hopes that a few hours I'll be greeted with pressure relief at the gas cap. The separator is disconnected, the check valve removed. The nipple at the fuel pickup is just capped off right now.

  2. #2
    FYI: New check valve works 100% better than the old. Tank now holds/builds pressure as required. Hope it starts better next time - I'll see this afternoon.

  3. #3

    Join Date
    Jan 2006
    Texas City, Texas
    Sounds like you are on track.

    The tank should hold about 3-4 lbs of pressure to help deliver the fuel to the carbs. The diaphrams in the carbs are designed to pump the fuel that is delivered to them, not suck fuel from the tank. Those few lbs that the check valve help to build in the tank is all that is needed to help make the fuel system work. Any extra pressure that is built up in the tank because of a hot garage or a hot summer day is just vented away via the check valve to maintain the required pressure.

    This may not be your problem, but putting your boat back to spec certainly will not hurt.

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